Anti-theft systems are currently in use by retail and other business establishments for monitoring merchandise by electronic detectors which include radio frequency (RF) reradiators or transponders encapsulated within tags attached to the merchandise. Should an attempt be made to remove a tagged article from the premises, an alarm is triggered when the article is carried through a RF surveillance zone near the store exit.
Various techniques are known for releasably attaching the transponder tags to merchandise such as garments. Typically, the garment is pierced by a tack whose pointed shank is received and gripped by a releasable, "one-way" fastener or latch spring concealed within the tag housing. The housing is designed to prevent access to the latch spring save by means of a special releasing mechanism maintained at the checkout counter and operable by sales or other authorized personnel. Examples of prior art security tags and releasing mechanisms are disclosed in U.S. Pat. No. 3,942,829 (Humble et al).
Although successful in reducing theft, many prior art devices have disadvantages. Not only are they occasionally defeated by pilferers but the procedure for releasing them from the garments tends to be awkward in that one hand is required to hold the tag in position relative to the tag-releasing mechanism while the other is needed to actuate the mechanism. The separation of the tag and garment thus entails a time consuming operation which is undesirable at retail checkout stations where many items must be processed as quickly as possible.
U.S. Pat. No. 3,973,418, issued to the present inventor, discloses an improvement in which the transponder tag is adapted to be released pneumatically thereby providing an additional degree of tamper resistance. Within the tag housing a pair of thin, plastic diaphragms acts to release the latch spring fastener when pressurized air is admitted through a pair of inlet openings each of which leads to a chamber adjacent one of the diaphragms. The diaphragms are oriented vertically, that is, generally parallel with the tack shank. However, such orientation of the diaphragms, which must be large enough to deflect sufficiently, results in a relatively bulky structure. Further, after a period of use, the integrity of the seals about the peripheries of the diaphragms tends to deteriorate thereby adversely affecting the release function. Last, the proper application of sealing compound to the diaphragms and the need for careful assembly of the components to assure leak-free operation adds substantially to the manufacturing cost of this tag.
In light of the foregoing, it is an overall object of the present invention to provide an improved, reusable anti-theft transponder tag that is of rugged construction and provides a high degree of security and resistance to tampering.
It is another object of the invention to provide a reusable security tag whose design facilitates and expedites its release and removal from an article by authorized personnel at the point of sale.
Yet another object of the invention is to provide a compact, low cost, pneumatically releasable transponder tag whose sealing elements are not subject to leakage even after extensive periods of use.